1. Field of the Invention
This invention relates to leaf spring suspension systems for trucks and trailers and the like wherein the leaves are mounted to prevent relative movement therebetween.
2. State of the Prior Art
Trucks and trailers typically employ multiple leaf-type vehicle suspensions in which a pair of axles are coupled to a trailer or truck bed through a load bearing trunnion. The axles are mounted at the ends of leaf springs which are secured at the central portion to the trunnion. The axles, which are secured at opposite ends of the leaf springs, are coupled to the leaves through axle housing connections. The end portions of the leaf springs are retained within the axle connection to permit motion therebetween.
During the operation of the truck or trailer, the springs are subjected to a relatively large flexing movement typically occurring during cornering of the vehicle or application of the brakes. Therefore, a certain amount of flexure is required between the springs so that some sliding movement between the leaves must be allowed. The turning of a vehicle, however, applies a lateral force on the leaf springs which subjects them to torsional stressing. This lateral force, which also stresses the axle connection housing, may lead to yielding or cracking at the end of the spring. Additionally, the lateral force tends to cause fanning or spreading of the springs.
One well-known spring mounting is disclosed in U.S. Pat. No. 2,539,091, issued Jan. 23, 1951, to Linke. In the Linke patent, a leaf spring suspension is retained in an axle connection which includes an upwardly extending pin received in apertures in the lower springs. Additionally, the lowermost springs include a hooked or curved end portion which aids in retaining the lowermost spring in the housing. The upstanding pin and the hooked end portion reduce relative movement between the springs as well as provide for safety by retaining the springs within the housing. If the lowermost spring should break, the pin, which is disposed within the two lower leaves, would prevent the leaves from sliding out of the axle connection.
The Van Raden U.S. Pat. No. 2,762,622, issued Sept. 11, 1956, also discloses a mounting for the end of a leaf spring suspension. The axle connection includes a base plate having an upstanding pin which is received within apertures in the lower springs of the leaf spring suspension. The pin has a convex surface portion which permits some longitudinal and transverse movement of the spring with respect to the base without inducing stresses within these springs. The pin extends into the two lowermost leaf springs so that if the pin breaks off at the base, longitudinal movement of the springs will be restrained relative to each other. In this way, the springs are prevented from slipping out of the housing.
The Linke and Van Raden patents both disclose spring retention means for the end of a leaf spring suspension system. The retention means prevents disengagement of the springs from the housing if the main leaf breaks and permits some flexing movement of the leaves during operation of the truck or trailer.
The Young U.S. Pat. No. 3,817,550 discloses a vehicle suspension system wherein the center portions of each spring include a cup seated in a recess in an adjacent spring and an aperture for receiving a bolt. The cup and bolt tend to maintain the springs in a vertical stack and limit lateral movement.